The invention relates to a process and an apparatus for coating a substrate with an organic coating by bringing the substrate into a coating chamber containing a gaseous hydrocarbon compound, in which the hydrocarbon compound can be decomposed by means of a cathode system having a magnet, while a plasma forming in the vicinity of the substrate can be excited by applying a radiofrequency voltage to the cathode system and holding the substrate directly in front of the cathode.
It is known to apply a thin coating to thin substrate, such as data storage or sound recording media, by means of an ionized atmosphere or by plasma-supported continuous vapor depositing, radiofrequency energy being used to excite the plasma while the chemical reaction is concentrated in front of the cathode by means of a magnet system. Since the storage density of magnetic storage media is very greatly determined by the thickness of the magnetic coating and the distance of the recording head from this coating, very thin coatings and especially close head spacing are desired. Experience shows, however, that this also increases the danger of damage to the coating by contact of the head with the coating, caused, for example, by vibration or by dust particles. On the other hand, however, the wear on the magnet head, especially in start-stop operation, must be kept as low as possible. Since it is possible with the prior-art coating methods to produce only a single coating with a very homogeneous structure, the manufacturer of such media has to compromise with regard to the coating quality.
The present invention sets for itself the task of creating a process and an apparatus which will be suitable on the one hand for producing a very thin coating which will be gentle on recording head, and on the other hand the task of producing a coating that will be comparatively insensitive to damage.